
// d3.tip
// Copyright (c) 2013 Justin Palmer
//
// Tooltips for d3.js SVG visualizations

// Public - contructs a new tooltip
//
// Returns a tip
d3.tip = function() {
    var direction = d3_tip_direction,
        offset    = d3_tip_offset,
        html      = d3_tip_html,
        node      = initNode(),
        svg       = null,
        point     = null,
        target    = null

    function tip(vis) {
        svg = getSVGNode(vis)
        point = svg.createSVGPoint()
        document.body.appendChild(node)
    }

    // Public - show the tooltip on the screen
    //
    // Returns a tip
    tip.show = function() {
        var args = Array.prototype.slice.call(arguments)
        if(args[args.length - 1] instanceof SVGElement) target = args.pop()

        var content = html.apply(this, args),
            poffset = offset.apply(this, args),
            dir     = direction.apply(this, args),
            nodel   = d3.select(node), i = 0,
            coords

        nodel.html(content)
            .style({ opacity: 1, 'pointer-events': 'all' })

        while(i--) nodel.classed(directions[i], false)
        coords = direction_callbacks.get(dir).apply(this)
        nodel.classed(dir, true).style({
            top: (coords.top +  poffset[0]) + 'px',
            left: (coords.left + poffset[1]) + 'px'
        })

        return tip
    }

    // Public - hide the tooltip
    //
    // Returns a tip
    tip.hide = function() {
        nodel = d3.select(node)
        nodel.style({ opacity: 0, 'pointer-events': 'none' })
        return tip
    }

    // Public: Proxy attr calls to the d3 tip container.  Sets or gets attribute value.
    //
    // n - name of the attribute
    // v - value of the attribute
    //
    // Returns tip or attribute value
    tip.attr = function(n, v) {
        if (arguments.length < 2 && typeof n === 'string') {
            return d3.select(node).attr(n)
        } else {
            var args =  Array.prototype.slice.call(arguments)
            d3.selection.prototype.attr.apply(d3.select(node), args)
        }

        return tip
    }

    // Public: Proxy style calls to the d3 tip container.  Sets or gets a style value.
    //
    // n - name of the property
    // v - value of the property
    //
    // Returns tip or style property value
    tip.style = function(n, v) {
        if (arguments.length < 2 && typeof n === 'string') {
            return d3.select(node).style(n)
        } else {
            var args =  Array.prototype.slice.call(arguments)
            d3.selection.prototype.style.apply(d3.select(node), args)
        }

        return tip
    }

    // Public: Set or get the direction of the tooltip
    //
    // v - One of n(north), s(south), e(east), or w(west), nw(northwest),
    //     sw(southwest), ne(northeast) or se(southeast)
    //
    // Returns tip or direction
    tip.direction = function(v) {
        if (!arguments.length) return direction
        direction = v == null ? v : d3.functor(v)

        return tip
    }

    // Public: Sets or gets the offset of the tip
    //
    // v - Array of [x, y] offset
    //
    // Returns offset or
    tip.offset = function(v) {
        if (!arguments.length) return offset
        offset = v == null ? v : d3.functor(v)

        return tip
    }

    // Public: sets or gets the html value of the tooltip
    //
    // v - String value of the tip
    //
    // Returns html value or tip
    tip.html = function(v) {
        if (!arguments.length) return html
        html = v == null ? v : d3.functor(v)

        return tip
    }

    function d3_tip_direction() { return 'n' }
    function d3_tip_offset() { return [0, 0] }
    function d3_tip_html() { return ' ' }

    var direction_callbacks = d3.map({
            n:  direction_n,
            s:  direction_s,
            e:  direction_e,
            w:  direction_w,
            nw: direction_nw,
            ne: direction_ne,
            sw: direction_sw,
            se: direction_se
        }),

        directions = direction_callbacks.keys()

    function direction_n() {
        var bbox = getScreenBBox()
        return {
            top:  bbox.n.y - node.offsetHeight,
            left: bbox.n.x - node.offsetWidth / 2
        }
    }

    function direction_s() {
        var bbox = getScreenBBox()
        return {
            top:  bbox.s.y,
            left: bbox.s.x - node.offsetWidth / 2
        }
    }

    function direction_e() {
        var bbox = getScreenBBox()
        return {
            top:  bbox.e.y - node.offsetHeight / 2,
            left: bbox.e.x
        }
    }

    function direction_w() {
        var bbox = getScreenBBox()
        return {
            top:  bbox.w.y - node.offsetHeight / 2,
            left: bbox.w.x - node.offsetWidth
        }
    }

    function direction_nw() {
        var bbox = getScreenBBox()
        return {
            top:  bbox.nw.y - node.offsetHeight,
            left: bbox.nw.x - node.offsetWidth
        }
    }

    function direction_ne() {
        var bbox = getScreenBBox()
        return {
            top:  bbox.ne.y - node.offsetHeight,
            left: bbox.ne.x
        }
    }

    function direction_sw() {
        var bbox = getScreenBBox()
        return {
            top:  bbox.sw.y,
            left: bbox.sw.x - node.offsetWidth
        }
    }

    function direction_se() {
        var bbox = getScreenBBox()
        return {
            top:  bbox.se.y,
            left: bbox.e.x
        }
    }

    function initNode() {
        var node = d3.select(document.createElement('div'))
        node.style({
            position: 'absolute',
            opacity: 0,
            pointerEvents: 'none',
            boxSizing: 'border-box'
        })

        return node.node()
    }

    function getSVGNode(el) {
        el = el.node()
        if(el.tagName.toLowerCase() == 'svg')
            return el

        return el.ownerSVGElement
    }

    // Private - gets the screen coordinates of a shape
    //
    // Given a shape on the screen, will return an SVGPoint for the directions
    // n(north), s(south), e(east), w(west), ne(northeast), se(southeast), nw(northwest),
    // sw(southwest).
    //
    //    +-+-+
    //    |   |
    //    +   +
    //    |   |
    //    +-+-+
    //
    // Returns an Object {n, s, e, w, nw, sw, ne, se}
    function getScreenBBox() {
        var targetel   = target || d3.event.target,
            bbox       = {},
            matrix     = targetel.getScreenCTM(),
            tbbox      = targetel.getBBox(),
            width      = tbbox.width,
            height     = tbbox.height,
            x          = tbbox.x,
            y          = tbbox.y,
            scrollTop  = document.documentElement.scrollTop || document.body.scrollTop,
            scrollLeft = document.documentElement.scrollLeft || document.body.scrollLeft


        point.x = x + scrollLeft
        point.y = y + scrollTop
        bbox.nw = point.matrixTransform(matrix)
        point.x += width
        bbox.ne = point.matrixTransform(matrix)
        point.y += height
        bbox.se = point.matrixTransform(matrix)
        point.x -= width
        bbox.sw = point.matrixTransform(matrix)
        point.y -= height / 2
        bbox.w  = point.matrixTransform(matrix)
        point.x += width
        bbox.e = point.matrixTransform(matrix)
        point.x -= width / 2
        point.y -= height / 2
        bbox.n = point.matrixTransform(matrix)
        point.y += height
        bbox.s = point.matrixTransform(matrix)

        return bbox
    }

    return tip
};